Creating a (reasonably) scientific public opinon poll online, and at low cost.

I’d like to be able to create an online poll that is as scientific (i.e., reflecting an accurate sample of a target audience) as possible, but on the cheap.

It seems to me I’ve heard of sites or services that have large numbers of members to whom you can pose questions, and get their answers, along with their demographic info so you can weight them appropriately.

But after Googling for a while, I can’t find anything quite like that.

There are sites like PollDaddy that let you put polls on your own Web site, but that’s not what I’m looking for. I’m looking for a large and diverse pool of people I can reach and survey.

Do you know of anything like that?

Creating the poll is one thing (see SurveyMonkey), getting it to reach a large group of diverse people is another thing entirely. I think that usually relies on your own publicity skills; in most cases I would find sites which people of my target are likely to visit and ask for permissions to post the poll (mine was for a marketing project).